Kirchhoff’s Voltage Law (KVL) – DC Circuits – Basic Electrical Engineering – First Year | Ekeeda.com
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Kirchhoff’s Voltage Law (KVL) – DC Circuits – Basic Electrical Engineering – First Year | Ekeeda.com


Hello friends in this video we are going to see the most fundamental law along with the Ohm’s law that we are supposed to use to solve a numerical not only a numerical but lots of concepts are based on these law so the law is kirchoff’s voltage law also known as KVL law states that algebraic sum of all the potential difference in a loop is always equal to zero so I repeat algebraic sum of potential differences in a closed loop circuit that in a closed circuit is equal to zero again the important concepts over here algebraic sum and what is the meaning of closed circuit so to elaborate this I will consider a simple circuit like this so I am having two batteries and three resistances connected in series like this so obviously it is a closed circuit and current will flow and because of this current there will be potential drop or voltage drop across these three resistances anyways these are the batteries having fixed polarities like this so we have to elaborate the concept of algebraic sum of potential differences so here in all I’m having one two three four five elements each element is having some or other voltage drop or it can also be called as voltage rise so I will right over here two concepts voltage drop and voltage rise so voltage drop I will consider as negative value and voltage rise I will consider as positive value now understand the meaning and difference between voltage drop and voltage rise suppose there is one element connected between these two point it could be anything it could be a battery or it could be a resistance and if in the direction of current if the two terminals having the polarities plus minus in the direction of current meaning the polarity is changing from plus to minus so whenever it is changing from plus to minus I will consider that particular potential as voltage drop likewise if in a direction of a current or pressing a closed circuit if I am having element voltage polarity changing from minus to plus it could be anything either a resistance or a battery I will consider that particular potential as voltage rise so lets apply this concept to the circuit now I am considering loop a b c d and if i tracing a part from a b c d back to the a I can have one two three four five potential differences so let’s start with r1 so in this direction it is changing from plus to minus plus to minus I consider as a voltage drop and I will consider that particular value as negative so for this resistance so voltage drop I will write as minus I into r1 current flowing through the r1 is I resistance values r1 so I to r1 is a voltage or a potential same way for r2 in this direction I am having plus to minus plus to minus is again a voltage drop which is a negative so minus I R2 third again a resistance having the same polarity plus minus so I will get minus I R3 now pay attention in the direction of current Here I am tracing all the voltage drops like this I am having plus minus once again plus minus so it is a voltage drop but hold on it is not a resistance it is a fixed voltage battery so I will have a minus sign because it is plus 2 minus but I should not write I into into in fact I should write only e 2 because that is a fixed voltage I am having irrespective of amount of current and finally in the direction of current I am having last potential as minus plus minus plus is voltage rise so voltage rights should be denoted Plus and mind you it is a battery so it will have simply plus e 1 equals to 0 so ultimately I can say these two are the battery voltages which I can Club together even minus e 2 equal to this 3 IR 1 IR 2 IR 3 are the voltage drops so I can write here I R1 plus I R2 plus I R3 so ultimately what is happening all the potential and amount of energy will remain conserved so KVL can also be considered as conservation of energy so batteries need to spend some energy and same energy will be consumed by all the resistors connected in a circuit so here we come to an end of a most fundamental law that is KVL from which we turn able to solve a problem which we will see in a subsequent videos thank you

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